I have been running de-googled LineageOS since before it renamed/reformed from CyanogenMod, so since somewhere around 2013/14. That has looked rather different depending on what exactly I need from my phone but I'll share what my current set up looks like.

First, I have don't use any kind of Google/Samsung/Apple Pay wallets so if you do, this may not be helpful; I've never looked into trying to get any of those working. Also, by "de-googled" I mean that I don't have GApps installed on my phone. I do have microG[0] installed as a Magisk[1]/LSPosed[2] module; this allows a few apps to believe I have GApps while most apps do not see/have access. I do not turn on microG for any apps (i.e. no connection to the Google servers/services via microG).

Most of my apps come from F-Droid[3], a few from Aurora Store[4] (a 3rd-party frontend for the Play Store that does not require either an account or GApps installed), a very few from FFupdater[5], and have played with using Obtanium[6] but currently only have one (weather) app updating via it. I have several different repositories configured in F-Droid but I don't generally keep mental track of which repository I am dependent on for which apps; the default, IzzyOnDroid[7], Bitwarden[8], NewPipe[9], microG[10], and Collabora[11] are some of them.

I have two banking apps installed via Aurora Store, one of which requires microG and root-hiding (via Magisk module) while the other doesn't require either. My browsers (Firefox, Firefox Klar, Brave) come from FFupdater and none require microG. My texting (QUIK SMS), email (K-9 Mail), TOTP authenticator (Aegis), password manager (Bitwarden), GPS/Maps (OsmAnd), file syncing (Nextcloud), notes (Nextcloud Notes), HN reader (HN), and Contacts/Calendar sync (DAVx5, ICSx5) apps all come via F-Droid (either the main repo or others). I have many others apps which come from F-Droid or Aurora Store but the above are my most used.

For file, calendar, notes, photo, & contact syncing, I have a Nextcloud server set up and find it to work quite well; the Nextcloud apps are also quite good. Someone who doesn't want to run their own could use a hosted account[12]. Contacts & calendars are synced to Nextcloud via DAVx5 & ICSx5.

The primary challenges I am aware of at this point are hardware (it is increasingly difficult to install LineageOS on most hardware due to bootloader locks), and navigation (OpenStreetMap data usually doesn't include addresses in the USA). For hardware, the solution is essentially just to properly research the phone you want to buy; I always make sure the model is well supported by LineageOS before purchasing and then tend to hang on to it for several years. For navigation, I usually find the address on my desktop or mobile browser (via DuckDuckGo) and then manually input the location into OsmAnd before the trip but I also keep WeGo Here maps installed in case I don't have time for that (it usually takes <2 minutes and rarely more than 5 to manually find & enter the address). Additionally, getting the one banking app to work without GApps was a pain in the butt initially (requiring testing several Magisk & LSPosed modules), but now it just works and I don't really think about it.

Overall, I don't find my version of de-googled to be a detriment; my phone is useful and I have more control over my data and over annoyances (such as unnecessary notifications) than I would otherwise.

[0] https://microg.org

[1] https://github.com/topjohnwu/Magisk

[2] https://github.com/mywalkb/LSPosed_mod

[3] https://f-droid.org

[4] https://aurorastore.org

[5] https://f-droid.org/packages/de.marmaro.krt.ffupdater | https://github.com/Tobi823/ffupdater

[6] https://f-droid.org/packages/dev.imranr.obtainium.fdroid/ | https://github.com/ImranR98/Obtainium

[7] https://apt.izzysoft.de/fdroid

[8] https://mobileapp.bitwarden.com/fdroid

[9] https://archive.newpipe.net/fdroid/repo

[10] https://microg.org/fdroid.html

[11] https://www.collaboraoffice.com/downloads/fdroid/repo

[12] https://nextcloud.com/sign-up